Rotary classifier for pulverizers and the like



Sept. 7, 1937. R. M. HARDGROVE -2,092,31o ROTARY CLASSiFIER FOR PULVERIZERS AND THE LIKE 2 sheets-sheer 1 Filed Dec. 20, 1964 0 H T WM Y E N m, U A

P 1937- y R. M. IY-IARDGROVE 2,092,310

ROTARY CLASSIFIER FOR PULVERIZERS AND THE LIKE Filed Dec. 20, 1934 2 Sheets-Sheet 2 I INVENTOR gaf .Har rave %TTORNEY Patented Sept. 7, 1937 AND rnr: LIKE Ralph M. Hardgrove, Westfield, N. J assignor to The Babcock 8; Wilcox Company, Newark, N. J., a corporation of New Jersey Application December 20, 1934, Serial No. 758,385

9 Claims.

My present invention relates in general to the construction of rotary classifiers and more particularly to rotary classifiers adapted for use in material pulverizers in which the pulverized material is removed by a gaseous carrier medium.

A main object of my invention is the provision of an improved construction of a rotary classifier which is characterized by its simple and low cost construction, efifective operation, low pressure loss, and avoidance of material deposits therein. A further object is the provision of improved driving means for a rotary classifier incorporated in a pulverizer whichare characterized by the substantial elimination of vibratory stresses therein,

the use therewith of efiective classifier sealing .provisions, and the elimination of gearing.

, The various features of novelty which characterize my invention'are pointed out with particularity in' the claims annexed to and forming a part of this specification. For a better understanding cf the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and. descriptive matter in which I have illustrated and described a preferred embodiment of my invention.

.Of the drawings: Fig. 1 .is a sectional elevation of a pulverizer incorporating my invention;

Fig. 2 is an enlarged .view of the rotary classiher shown in Fig. l; and v Fig. 3 is a section on the line i-t of Fig. 2. In the drawings, I have illustrated a pulverizer incorporating a rotary classifier constructed and arranged in accordance with my invention. As shown, the pulverizer has a vertically arranged sectional casing it of circular cross-section mounted on a suitable foundation Ill and enclosing a plurality of relatively movable grinding .parts which cooperate to form a plurality of material grinding stages. The grinding parts include a non-rotary floating upper grinding ring it, a rotary floating intermediate grinding ring it, and a stationary lower grinding ring Ml, between which are positioned upper and lower circular rows of grinding balls it.

Rotation of the intermediate grinding ring and contacting rows of balls is effectedfiby a drive shaft lfi'arranged axially of the rows of balls and held in vertical alignment by an upper roller bearing ll and a bottom thrust bearing 118. At its upper end the drive shaft carries a drive yoke having one'or more plates H on its outer side 5 positioned between corresponding pairs of plates 22 on the inner side of theintermediate ring and providing a floating drive connection for the intermediate ring. A suitable grinding pressure is superposed on the grinding parts by a series of coiled springs I9 acting on the upper ring l2. At the lower end' of the casing I0 is formed an 5 annular box 23 having an inlet 24 thereto for the delivery of any suitable gaseous carrier medium, such as preheated air. The air box 23 is connected by radial passages 25 to the inner side of the lower row of balls. Transverse ports 26 10 are arranged in the intermediate ring for the outward passage of material-laden air. A pipe 27 is connected to the casing in above the grinding parts for the delivery of the material to be pulverized onto a conical plate it at the inner 15 side of the upper row of balls. With the foregoing construction and arrangement of the grinding parts, the material passes outwardly through the upper row of balls and then inwardly through the lower row, and a stream of air is passed upwardly to the casing, sweeping up material from the inner side of the lower row of balls before passing outwardly through theports it and then upwardly past the outer side of the upper row of balls.

In the pulverizer shown, the top wall it of the casing is formed with asymmetrically arranged group of outlets til for the material-laden air. Each of the outlets is provided with a swingable externally operated valve disc it for regulating the delivery of pulverized material.

The material in suspension in the ascending air stream includes a substantial amount of oversize or coarse particles. Various types of classifying devices have heretofore been used in the upper section of the pulverizer for separating oversize material from the air stream before it leaves the pulverizer and returning the coarse material separated to the grinding section. In the present k construction, a classifier of the rotary type is arranged in the upper part of the pulverizer cas-- ing in the path of the material-laden air stream to the casing outlets til. As shown in Figs. 2 and 3, the classifier is formed by a horizontally arranged substantially conical bottom plate it flaring downwardly for a distance outside the area occupied by the group of outlets it, so that the air stream will be forced to pass outwardly around the plate it. The plate 33 has an inclination of about 27 to the horizontal, while the extreme outer portion 33 of the plate preferably has a greater inclination, as shown. An annular top plate it is arranged in vertical alignment with the section it of the bottom plate and provided with a vertical flange 34 extending upwardly at its inner side. The flange 3% fits rotatably within the reduced lower end of a circular seal plate 35 extending downwardly from the casing top Wall 29 and surrounding the outlets Sll so that short circuiting of the classifier is prevented by the effective seal so provided. The seal plate 35 forms in effect a common extension for the outlets 30. Between and connected to the top plate 34 and the bottom plate section is arranged a series of vertically extending blades The blades 36 are arranged in vertical planes at similar acute angles to the circumferences of the plates 33 and 3 and with the trailing edge of the blades in vertical alignment with the circumference of the plate 33.

With the classifier described in operation, the substantially radial entry of all portions of the material-laden air into the classifier insures that a constant centrifugal force will be exerted on all of the particles of material in the entering air stream opposing their entry. As the centrifugal effect on and the momentum of the suspended particles will be proportional to the mass of the particles, the velocity of the air stream can be suitably controlled so that the centrifugal effect will prevent particles of less than the desired degree of fineness from entering the interior of the classifier. A definite separation or classification of the suspended material can be thereby effected. Rotation of the classifier is advantageously secured in' accordance with my invention by securing the plate 33 to a split clamp 46 on a vertically arranged drive shaft 40. The shaft 40 is connected to form a rigid extension of the drive shaft l6, and is secured in vertical alignment through a clutch plate 42 fastened to the top of the drive yoke 20. The lower end of the shaft 40 has a transverse recess 43 receiving a correspondingly shaped ridge 44 on the plate 42. A dowel pin 45 holds the engaging portions in position. The upper end of the shaft 40 extends through the top wall of the casing and is positioned within a roller bearing 46. mounted thereon. The form of connection of the classifier drive shaft to the pulverizer drive shaft and the mounting of the two drive shafts insures a classifier drive which is substantially free from vibratory stresses, as would occur, for example, if the' shaft 40 were connected to the rotary intermediate ring.

In the operation of the pulverizer described, a substantially annular stream of material-laden air will ascend at a predetermined velocity in the casing l0 towards the outlets 30. The air stream will be directed towards the sides of the casing by the arrangement of the rotating plate 33. The pressure differential through the pulverizer will cause the stream of air to move inwardly through the passages between the moving blades 36, during which movement the suspended particles of material will be subjected tothe centrifugal effect of the classifier. The centrifugal action will cause the oversize particles to be thrown outwardly toward the sides of the casing and to drop to the lower or grinding section of the casing. The centrifugal effect however, on

the particles of desired fineness is not sufficient.

to cause those particles to be thrown out, and they remain in suspension, passing inwardly through the interbladepassages to the interior of the classifier. Some of the material tends to separate within the classifier and deposit on the bottom plate 33. The conical shape of that plate however, causes any deposited material to flow downwardly into the bladed section from which aoaasio it is thrown outwardly. A useless load on the drive shafts and clogging of the interblade passages is thereby avoided. The shape of the bottom and top plates is also advantageous inproducing an air fiow through the classifier with a minimum pressure loss.

While in. accordance with the provisions of the statutes I have illustrated and described herein the best form of my invention known to me, those skilled in the art will understand that changes may be made in the form of the apparatus and character of the carrier medium disclosed without departing from the spirit of the invention covered by my claims, and. that certain features of my invention may sometimes be used without a corresponding use of other features. In my claims, the word air is used generically to cover any gaseous carrier medium suitable for removing pulverized material in the manner described.

I claim:

1. A pulverizer comprising a casing having an outlet for material-laden air in the top thereof, relatively movable grinding parts within said casing and cooperating to form a grinding stage, a vertically arranged drive shaft for effecting relative movement of said grinding parts and having an upper por'tion adjacent said outlet, means for passing a stream of air upwardly in said casing towards said outlet sweeping up pulverized material from said grinding stage during its passage, and a rotary material classifier in the path of the material-laden air adjacent to said outlet having a horizontally arranged conical plate mounted on said drive shaft and extending out wardly beyond and below said outlet, and a series of arcuately spaced blades mounted on the upper side of said plate beyond said outlet and having passages therebetween communicating with said outlet.

2. A pulverlzer comprising a. substantially circular casing having an outlet for material-laden air in the top thereof, relatively movable grinding parts within said casing and cooperating to form a grinding stage, a vertically arranged drive shaft for effecting relative movement of said grinding parts and having an upper portion adjacent said outlet, means for passing a stream of air upwardly in said casing towards said outlet sweeping up pulverized material from said grinding stage during its passage, and a rotary material classlfier in the path of the material-laden air adjacent to said outlet having a horizontally arranged conical plate mounted on said drive shaft and extending outwardly beyond and below said outlet, and a series of arcuately spaced blades vertically mounted 6n the upper side of said plate outwardly beyond said outlet at an angle to the circumference thereof and having passages therebetween communicating with said outlet.

3. A pulverizer comprising a. substantially circular casing having an outlet for material-laden air in the top thereof, relatively movable grinding parts within said casing and cooperating to form a grinding stage, a vertically arranged drive shaft for effecting relative movement of said grinding parts, bearing means for holding said drive shaft in vertical alignment, 9. vertical shaft forming an extension of and directlyconnected to said drive shaft and having its upper end adjacent said outlet, a. bearing arranged to receive the upper end of said drive shaft extension, means for passing a stream of air upwardly in said casing towards said outlet sweeping ,up pulv aooaaio :llt

verized material fr om said grinding stage during its passage, and a rotary material classifier in the path of the material-laden air adjacent to said outlet having a horizontally arranged imperforate conical plate mounted on said drive shaft and extending outwardly beyond and below said outlet, and a series'of arcuately spaced blades vertically mountedon' said plate outwardly beyond said outlet at an angle to the circumference thereof and having passages therebetween communicating with said outlet.

4. In combination, a substantially circular casing having an outlet for material-laden air in the top thereof, and a rotary material classifier in said casing in the path of the material-laden air adjacent tosaid outlet having a vertically arranged drive shaft, a horizontally arranged imperforate conical plate mounted on said drive shaft and extending outwardly beyond and below said outlet, and a series of arcuately spaced vertically extending blades mounted on the upper side of said plate outwardly beyond said outlet at an oblique angle to the circumference of said plate and having passageways therebetween communicating with said outlet.

5. A pulverizer comprising a casing having an outletfor material-laden air in the upper part thereof, upper and lower horizontally arranged grinding rings within said casing, a circular row of rolling grinding elements positioned between said rings and'cooperating therewith to form a grinding stage, a verticallyfixed drive shaft hav-- ing a floating drive connection with said upper ring; drive means operatively connected with the lower end of said drive shaft, means for ,di-

.recting a stream of air upwardly in said casing towards said outlet and sweeping up pulverized material from said grinding stage during its passage; a rotary material classifier in the path of the material-laden air having a horizontally arranged substantially imperforate plate mounted on said drive shaft and extending outwardly below said outlet, a series of arcuately spaced blades vertically mounted on the upper side of said'plate and having passages therebetwben communicating with said outlet, and sealing means for preventing the passage of materialladen air to said outlet other than inwardly through said classifier interblade passages.

6. A pulverizer comprising a casing having an outlet for material-laden air in the upper part thereof, upper and lower horizontally arranged grinding rings within said casing, a circular row of rolling grinding elements positioned between said rings and cooperating therewith to form a grinding stage, a vertically fixed drive shaft having a floating drive connection with said upper ring, drive means operatively connected with the lower end of said drive shaft, a vertical shaft forming an extension of and operatively connected to said drive shaft and having its upper end adjacent said outlet, means for directing a stream of air upwardly in said casing towards said outlet and sweeping up pulverized material from said grinding stage during its passage, a rotary material classifier in the path of thematerial-laden air having a horizontally arranged substantially imperforate plate mounted on said drive shaft extension and extending outwardly below said outlet, and a series of arcuately spaced blades vertically mounted pm the upper side of said plate and having passages therebetween communicating with said outlet.

7. A pulverizer comprising a casing having an outlet for material-laden air in the upper part thereof, upper and lower horizontally arranged grinding rings within said casing, a circular row of rolling grinding elements positioned between said rings and cooperating therewith to form a grinding stage, a vertically fixed drive shaft having a floating drive connection with said upper ring, drive means operatively connected with the lower end of said drive shaft, 2. vertical shaft forming an extension of and directly connected to said drive shaft andhaving its upper end adjacent said outlet, a bearing arranged to receive the upper end of said drive shaft extension, means for directing a stream of air upwardly in said casing towards said outlet and sweeping up pulverized material from said grinding stage during its passage, a rotary material classifier in the path of the material-laden air having a horizontlly arranged substantially imperforate plate mounted on said drive shaft extension and extending outwardly below said outlet, a series of arcuately spaced blades vertically mounted on the upper side of said plate and having passages therebetween communicating with said outlet, and sealing means for preventing the passage of material-laden air to said outlet other than inwardly through said classifier interblade passages.

8. In combination, a casing having a plurality of outlets for material-laden air in the top thereof, a seal plate surrounding said outlets and forming a common extension thereof within said casing, and a rotary material classifier in said casing in the path of the material-laden air adjacent to said outlets having a drive shaft, a substantially imperforate conical plate mounted on said drive shaft and extending below said seal plate, and a series of arcuately spaced blades mounted on the upper side of said plate and having passageways therebetween communicating with said outlets, said classifier and seal plate being so relatively arranged as to require all of the material-laden air passing to said outlets to flow inwardly through said classifier interblade passages.

9. In combination, a casing having an outlet for material-laden air in the upper part thereof, and a rotary material classifier in said casing in the path of the material-laden air adjacent to said outlet having a vertically arranged drive shaft, a horizontally arranged substantially imperforate conical plate mounted on said drive shaft and extending outwardly beyond and below said outlet, a series of arcuately spaced vertically extending blades mounted on the upper side of said plate outwardly beyond said outlet and having passageways therebetween communicating with said outlet, the annular portion of said plate carrying said blades having a greater outward slope than the inner portion thereof, and said classifier and outlet being so relatively arranged as to require all of the material-laden air passing to said outlet to flow inwardly through said classifier interblade passages. 

